The aquatint screen is essential needed to structure the polymer plate and achieve the reproduction of continuous tone images (with tonal scaling). Whether working with autographics image positives or with digital image positives, the use of a stochastic screen is necessary. The irregular grain of the aquatint screen is composed of randomly arranged microscopic dots that help the appearance of image tonal gradations. In short, the stochastic or aquatint screen positive helps us to take advantage of all those grays that would not appear otherwise. Also, avoid open bites and irregular white blotches in areas close to blacks.
In the jargon of printmakers it is known as aquatint screen by analogy to the chalcographic technique, where random dots of colofonian dusted resin are arranged on metal plates, accommodating the base for the construction of tonal images depending of acid work. In our case, the plot is exposed by means of a UV light unit on the polymer plates prior to the analog or digital positive.
In short, the stochastic raster positive is used to convert continuous-tone images to discontinuous-tone images. In this way, these types of images will be feasible to stamp with photopolymer plates.
Due to the demand of some customers, the Rittagraf technical team has generated 3 different types of aquatint screens. The three differ in the size of the plot point.
- Heavy Dot Screen: 84 micron size dot
- Medium Dot Screen: 40 micron size dot
- Fine Dot Screen: 31 micron size dot
The screen greatly affects the final quality of our photopolymer plate. The tonal range that we can achieve in photogravure printing depends on the structure and layout of the plot. Without the use of a stochastic screen, our photo-etchings prints would be too contrasty, missing out on the wide tonal ranges that can be achieved with polymer. To learn more about the use and of this type of patterns in photopolymer plates, we recommend the most complete study and book of photogravure by our friend Ramón Freire: The graphic act as construction. Autographic positive and photopolymer plate (spanish language). Among others, we also recommend you: Polymer Photogravure, A new Method for Photographers and Graphic Artists, from Taneli Eskola and Kari Holopinen.